| The safety of drinking water is associated with our health and life security, so water treatment plant and water distribution network play an important role in ensuring that residents have safe drinking water. Yet, drinking water is risky because of secondary pollution in the distribution network, especially the microorganisms recolonization and biofilms into water after shedding.Based on the simulant water distribution pipes and an actual pipe, the microbial diversity of biofilms and its influencing factors was studied, and the mechanism of particulate matter on biofilm was discussed, with the object of biofilms, particles, and extracellular polymeric substances(EPS). High throughput sequencing, flow cytometry, Three-dimensional excitation emission matrix fluorescence spectrum, and Fourier transform infrared spectroscopy were used. The results are summarized as follows:1. In the actual cast iron pipe, with the increase of the runtime, particle concentration gradually comes to stability; with the increase of the pressure and distribution distance, particle concentration increases, which provokes a further secondary pollution.2. Compared with the actual pipe network, the running time of experimental device was shorter. However, the biofilm has a rich diversity of species, and a variety of pathogenic microorganisms such as Pseudomonas and Burkholderia was found. In phylum level, Firmicutes and Proteobacteria are the most, with the relative abundance of 94%~98%. And in species level, Bacillus is the most dominant strain in biofilms communities, followed by other four significantly different dominant strains.3. Biofilms diversity of ultrafiltration process was relatively lower than traditional process, as well as PVC pipe lower than cast iron pipe, the top lower than the bottom in cast iron pipe, actual PVC pipe(supplying raw water for the experiment)lower than the simulant PVC pipe. There are many factors influencing the biofilm. In Phylum level, pipe material is the most significant factor for biofilm diversity; in species level, the main factor is not obvious.4. With the increase of the particle concentration, biomass increases and then decreases. The reason is: In low concentrations, particles combined mainly with bacteria by interaction between particle and EPS, forming a stable biofilm structure;in high concentrations, particles gather each other by EPS, not combined with biofilm,and the structure is not stable.5. The reason that particles contribute to the stable biofilms is preliminary considered as followed: Particle with positive charge on the surface has a strong power in the adsorption for the opposite-charged EPS forming a stable chemical bond.OH bond of Extracellular polymeric substances is the key functional group.Results of this paper has certain theoretical guiding significance in controlling biofilm formation, ensuring the safety of drinking water microbes, and reducing secondary pollution. |
